BRIDGE UPDATE

More preparations will be made this week for the Big Switch on June 19. That's when Tacoma-bound traffic on the Gig Harbor side of the bridge will be moved across the median onto the future westbound lanes of Highway 16. All traffic east of the 36th Street onramp will stay on that side of the median until the new bridge opens in 2007. The idea is to give crews room to work on the new toll plaza and eastbound bridge approach.

Crews also will be grading the new westbound mainline on the Gig Harbor side, in the vicinity of the weigh station.

Anchorages: Crews will continue installing anchor tubes on the Tacoma side and forming up walls on the Gig Harbor side.

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Caissons: Concrete crews on the Gig Harbor side poured the first 2 1/2 feet of the distribution cap on Friday. This week they'll put in steel for the next pour. That tower foundation should be finished June 16.

Meanwhile, dredging will continue on the Tacoma side. That caisson is sinking about 18 inches a day, with about 25 feet to go.

Q&A

Q. What are those three blue cranes doing north of the existing bridge on the Tacoma side?

A. Seismic retrofitting. Tacoma Narrows Constructors is drilling four 50-foot shafts, each 10 feet in diameter, and filling them with reinforced concrete. The columns will be tied to the approach structure of the existing bridge to help it withstand earthquakes.